1. Field of the Invention
The present invention relates to a compressor suitable for use in a super-critical refrigerating cycle in which a discharge pressure of the compressor is higher than a refrigerant critical pressure.
2. Description of Related Art
JP-A-57-148087 discloses a scroll-type compressor used for a refrigerating cycle. In this scroll-type compressor, a spherical roller receives a thrust force. The thrust force is an element force of the compression counter-force acting on a movable scroll, which is perpendicular to the orbital direction of the movable scroll. The spherical roller rolls to support and allow the movable scroll to orbit.
A discharge pressure of a compressor in a super-critical refrigerating cycle is 7-10 times higher than that in a conventional refrigerating cycle using a flon as a refrigerant.
Therefore, when the compressor disclosed in JP-A-57-148087 is applied to the super-critical refrigerating cycle, because a contact surface pressure of the spherical roller is large, the spherical roller and a surface contacting the roller can be damaged, thereby reducing the reliability and durability of the compressor.
To address this problem, it is considerable to enlarge the diameter of the spherical roller can be damaged or the number of rollers increased. However, this causes the compressor to be enlarged.